1. Technical Field
The present invention relates to a pattern forming method, a liquid droplet discharging apparatus, and an electrooptical device.
2. Related Art
Liquid crystal displays use an oriented film subjected to orientation treatment to determine the orientation direction of liquid crystal molecules. As a method for producing the oriented film, an inkjet method has been eagerly developed that uses a liquid droplet discharging apparatus to improve productivity and reduce production costs.
The discharging apparatus includes nozzles that discharge liquid droplets containing an oriented-film material and a discharging head with the nozzles moving relatively with respect to a substrate. The head and the substrate are relatively moved in a main-scanning direction, whereby selected nozzles discharge the liquid droplets. Then, fluid layers containing the oriented-film material are sequentially drawn in the main-scanning direction on the substrate and dried to be formed into the oriented film.
In the discharging apparatus, when the oriented film becomes larger than a scanning width of the discharging head, the head and the substrate are relatively moved in a sub-scanning direction intersecting with the main-scanning direction and then again are relatively moved in the main-scanning direction. In short, the head performs a line-feeding scanning. In the line-feeding scanning, the droplets discharged by the former scanning begin to dry faster than those discharged by the latter scanning. As a result, a part of fluid material landed on the latter scanning region is flown to a former-scanning region, thereby causing the formation of streak-like stepped portions having a thickness continuing in the main-scanning direction at the boundary between scanning routes. The stepped portions are hereinafter referred to simply as “streak variation”.
Thus, regarding the inkjet method, there have conventionally been proposed techniques for eliminating the streak variation to improve thickness uniformity of the oriented film. For example, in JP-A-2003-284992, there are provided rollers apart from a substrate surface by a predetermined distance. The rollers are pressed onto the entire surface of a coating layer formed on the substrate surface, so that the rollers' physical forces correct the thickness of the coating layer.
In the above technique, however, when correcting the thickness thereof, the rollers are pressed onto the entire coating layer, whereby most of the fluid material contained in the layer adheres to the rollers and is removed from the substrate surface. Consequently, using the technique in the liquid droplet discharging apparatuses increases the using amount of the oriented-film material. This hinders raw material reduction, which is an advantage of the inkjet method.